This paper investigates the effect of trapezoidal baffles inside a planar-type solid oxide fuel cell. To achieve the objective, four cases are proposed: (1) simple planar geometry as a base case, (2) trapezoidal baffles inside the fuel channel, (3) trapezoidal baffles inside the air channel, and (4) trapezoidal baffles in both fuel and air channels. The height of the trapezoidal baffles inside the channels of the solid oxide fuel cell increases along the direction of the fluid flow. The numerical investigation is based on a three-dimensional computational fluid dynamics (CFD) model that takes into account the phenomenon of mass transfer, heat transfer, species transport, and electrochemical reactions. A detailed comparison of the performance between the four cases of the fuel cell is provided in terms of power density, fluid flow, species concentration, temperature distributions, and electric fields at a variable current density and a fixed power density of 3000 W/m2. The results show that the power density, the velocity, the availability of the hydrogen and oxygen species on the electrodes-electrolyte interfaces increases for case 2, case 3, and case 4, respectively, in comparison to case 1. Finally, the average temperature of the electrode–electrolyte interface is reduced with the baffles, and it is concluded that the configuration with baffles inside the air channel (case 3) shows better results in terms of the increment of the power density and the decrement of the average temperature.